Rio de Janeiro, Brazil – In a groundbreaking study, scientists from the Oswaldo Cruz Foundation have discovered cocaine in the tissues of sharks living off the coast of Rio de Janeiro. This marks the first time that the drug has been detected in free-ranging sharks, raising significant concerns about the impact of human drug use on marine ecosystems.

The study, published in the journal Science of the Total Environment, involved testing 13 Brazilian sharpnose sharks. Cocaine was found in both the liver and muscle tissue of all the sharks. The levels of cocaine were approximately three times higher in muscle tissue than in liver tissue, with female sharks exhibiting higher concentrations compared to males.

Sources of Contamination

According to the study, the contamination primarily stems from sewage discharges from human drug use and illegal drug production. Unlike regions such as Mexico and Florida, where drug traffickers often dump bales of cocaine into the sea, the Brazilian sharks are primarily affected by pollutants entering the ocean through wastewater. Enrico Mendes Saggioro, an ecotoxicologist and co-author of the study, emphasized that the prevalence of cocaine in the waters off Rio de Janeiro is due to increased consumption and inadequate sewage treatment infrastructure.

Environmental and Health Implications

While the study did not directly investigate the effects of cocaine on the health of the sharks, previous research has shown that the drug can harm other aquatic animals, such as fish and mussels. The researchers believe that cocaine could have deleterious physiological effects on sharks, potentially affecting their behavior and overall health. “Cocaine targets the brain, and hyperactive and erratic behavior has been noted in other animals,” said Mendes Saggioro and co-author Rachel Ann Hauser Davis.

The contamination of marine life with cocaine also poses potential risks to human health, as sharks are routinely consumed by humans in Brazil and other countries. The researchers plan to expand their studies to other species, including rays and migratory fish, to better understand the extent of cocaine accumulation in marine ecosystems.

Global Context

This study adds to a growing body of evidence demonstrating the pervasive impact of human drug use on aquatic environments. In 2021, researchers found that brown trout could become addicted to methamphetamine present in waterways. Similar studies in the United Kingdom and the United States have detected traces of illicit drugs, pharmaceuticals, and pesticides in freshwater shrimp and mussels, respectively.

The findings from Brazil highlight the urgent need for improved wastewater treatment infrastructure and more stringent environmental regulations to mitigate the impact of human pollutants on marine life. As the researchers continue their investigations, the full extent of the ecological and health consequences of cocaine contamination in the ocean remains to be seen.

Next Steps

Moving forward, the research team aims to analyze other shark species and rays living in river estuaries. They also plan to study migratory fish, such as mullet, to determine if their migratory behavior influences cocaine accumulation. The goal is to develop a comprehensive understanding of how widespread this contamination is and to inform strategies to protect marine life from drug pollution.

The study underscores the interconnectedness of human activities and environmental health, reminding us of the far-reaching impacts of our actions on the natural world.